In this description, for halogenated-hydrocarbon, an abbreviated name of a compound is described between parentheses after the compound name, and the abbreviated name is used in place of the compound name as needed in this description.
Generally, a gasoline vehicle travels by combusting gasoline being a fuel. For heating in the gasoline vehicle, a method is employed which utilizes waste heat of the gasoline combustion in the engine and heats air in the vehicle using heat of cooling water for cooling the engine. Further, for cooling in the gasoline vehicle, a method is employed which utilizes heat pump and cools the air in the vehicle using evaporation heat generated by evaporating coolant being a working fluid in an evaporator.
Conventionally, chlorofluorocarbon (CFC) such as dichlorodifluoromethane has been used as an air-conditioner working fluid for gasoline vehicle. However, CFC is pointed out as exerting influence on the ozone layer in the stratosphere, and is a subject to regulation at present.
From the above background, conventionally, hydrofluorocarbon (HFC) exerting less influence on the ozone layer, for example, 1,1,1,2-tetrafluoroethane (HFC-134a) has been widely used in place of CFC as the air-conditioner working fluid for gasoline vehicle.
HFC, however, is pointed out as possibly being a cause of global warming. For example, HFC-134a has a global warming potential (GWP) as high as 1430, and it is thus required to develop a low GWP working fluid. At this time, it is required to develop a working fluid allowing a device which has been used till now to be continuously used as it is, only by replacing HFC-134a.
Recently, expectations are concentrated on HFC having a carbon-carbon double bond that is likely to be decomposed by OH radicals in the air, namely, hydrofluoroolefin (HFO), as the working fluid exerting less influence on the ozone layer and less influence on global warming. In this description, saturated HFC is called HFC and discriminated from HFO unless otherwise stated. Further, HFC may be clearly described as saturated hydrofluorocarbon in some cases.
As the air-conditioner working fluid for gasoline vehicle capable of replacing the above HFC-134a, tetrafluoropropene, in particular, 2,3,3,3-tetrafluoropropene (HFO-1234yf) has been proposed (Patent Reference 1 (Japanese Patent No. 4571183)). HFO-1234yf has an extremely low GWP of 4 though having equivalent performance with that of HFC-134a.
On the other hand, the electric vehicle increases in penetration rate recently has a smaller amount of waste heat than that of the gasoline vehicle and cannot utilize waste heat of the engine for heating. Therefore, it is desired to develop an air-conditioner for electric vehicle utilizing heat pump also for heating in addition to cooling.
However, HFC-134a and HFO-1234yf are not sufficient in characteristics such as cycle performance as the air-conditioner working fluid for electric vehicle.